Yeomans J S
Department of Psychology, University of Toronto, Ontario, Canada.
Neurosci Biobehav Rev. 1989 Summer-Fall;13(2-3):91-8. doi: 10.1016/s0149-7634(89)80016-8.
The directly activated substrates for medial forebrain bundle (MFB) self-stimulation are primarily low threshold, myelinated axons with absolute refractory periods of 0.4 to 1.2 msec, conduction velocities of 1 to 8 m/sec and current-distance constants of 1000 to 3000 microA/mm2. When small electrode tips or high currents are used, however, a second population of long refractory period (1.2 to 5 msec) axons is added. The excitability properties of this second population are almost identical with those of dopamine (DA) axons. Furthermore, the long-refractory period effects of MFB self-stimulation are reduced, but not completely blocked, by peripheral injections of alpha-flupenthixol, suggesting that dopamine axons make small contributions to MFB self-stimulation when small tips are used. Collision data, strength-duration data and refractory period data in various self-stimulation experiments are compared. Asymmetric collision effects, recently observed in cortical and striatal sites mediating electrically evoked turning, may help determine where synapses are located in circuits mediating electrically evoked behaviors. A neural model of symmetric, asymmetric and mixed collision is proposed.
内侧前脑束（MFB）自我刺激的直接激活底物主要是低阈值、有髓鞘的轴突，其绝对不应期为0.4至1.2毫秒，传导速度为1至8米/秒，电流-距离常数为1000至3000微安/平方毫米。然而，当使用小电极尖端或高电流时，会增加第二批长不应期（1.2至5毫秒）的轴突。第二批轴突的兴奋性特性与多巴胺（DA）轴突几乎相同。此外，外周注射α-氟奋乃静可降低但不能完全阻断MFB自我刺激的长不应期效应，这表明当使用小电极尖端时，多巴胺轴突对MFB自我刺激的贡献较小。比较了各种自我刺激实验中的碰撞数据、强度-持续时间数据和不应期数据。最近在介导电诱发转向的皮质和纹状体部位观察到的不对称碰撞效应，可能有助于确定介导电诱发行为的回路中突触的位置。提出了对称、不对称和混合碰撞的神经模型。
